No, it is not. It is no more based on a true story than the Blair Witch Project. It is one of those movies that the directors and producers spread rumors about it being based on a true story, but in reality it is not. When you have a horror movie and can get people to think that it might have been real, then it sells more tickets.
Who ever said this is fake is a f***king moron! An outbreak happened in la around 2006. No one lived. Look it up instead of trying to make accusations!